The main difference between a concept and a variable is measurability. Concepts are I mental images or perceptions and therefore their meanings vary markedly from individual to individual, whereas variables are measurable, though, of course, with varying degrees of accuracy depending upon the measurement scale used. A concept as such cannot be measured, whereas a variable can be subjected to measurement by crude/refined or subjective/objective units of measurement. Concepts are subjective impressions which, if measured as such, would cause problems in comparing responses obtained from different respondents. According to Young (1966: 18):